Microfluidic Approach for Evaluating the Solubility of Crude Oil Asphaltenes

In this paper, we describe a microfluidic approach for measuring the solubility of asphaltenes in a sample of crude oil. The solubility parameter is an important property in assessing stability of asphaltenes in crude oils and crude mixtures, particularly when blending different oils or adding diluents. A range of solvent–precipitant mixtures are added to the crude oil, which modifies the native solubility properties, and the degree of asphaltene precipitation is monitored by the change in optical absorbance for each chosen solvent volume fraction. The microfluidic solubility profiles acquired in hours are compared to conventional gravimetric measurements obtained over days and demonstrate excellent agreement. We also show the application of the data generated for tuning solubility parameter-based thermodynamic models of asphaltene precipitation in mixtures of solvents and precipitants. The microfluidic data were used to determine the asphaltene solubility parameter that ranged from 20 to 23 MPa1/2 for the crude oils used in this study, in agreement with previous reports. The more efficient use of labor and the reduction in measurement time enabled by the microfluidic method will allow for more frequent asphaltene characterization for evaluating stability and tuning models.